Genuinely think it's supposed to be like the show Revolution. Where the power is being drained by magic nanobots, but subsequent aurorae are like the magic pendants that give power back for some reason.

That was a shit show. It seems as if the designers took the premise, which was actually good, and made it not shit, by having it take place in Canada. Everything's better in Canada! 

I think it affected something else, something long-term, that causes everything to fail to hold a charge. But subsequent aurorae charges the atmosphere, and devices like the flashlight are powered by that. Not sure, and I'm glad I don't know, because if they explained it, it would probably just ruin it. Keep the mechanics a mystery, it makes it more interesting.